In order to reduce the energy consumption of vehicles and to improve convenience for a driver, a system in which an alternate route having no traffic congestion is calculated based on road traffic information so as to be presented to a driver has been proposed. However, when multiple drivers travel the route having no traffic congestion in accordance with the presented route, there is a possibility of concentration of vehicles in the route, thereby causing an occurrence of traffic congestion again in the other route which is presented in order to ease the traffic congestion, and thus, the system is not a fundamental solution to the optimization of traffic flow and minimization of the energy consumption of the vehicles.
PTL 1 discloses that an optimal route for the vehicle is determined by using information on a current traffic flow received from each of the vehicles. In order to achieve the optimization of traffic flow, after the route is determined, if an unpredicted change in the traffic flow is detected, the system functions to designate a new optimal route for the vehicle again replacing the old route.
PTL 2 discloses a function of selecting the optimal route performed by using altitude information of a road map in order to minimize the energy consumption of vehicles.